1. Field of the Invention
The invention relates to an antiperspirant in the form of a transparent gelled stick.
2. The Prior Art
Solid antiperspirant formulations generally fall within two broad categories--suspensoid sticks and gelled alcoholic sticks. Suspensoid sticks usually consist of acidic antiperspirant actives suspended in a matrix formed by a wax in an emollient. Illustrative of this category are the formulations presented in U.S. Pat. No. 4,431,837 (Geria). Example 7 of this patent describes an antiperspirant stick suspending Rezal (aluminum/zirconium tetrachlorhydrex glycine complex) in a wax matrix of stearyl alcohol and Castorwax MP 80 Volatile silicone and C.sub.8 -C.sub.18 aliphatic hydrocarbon ethoxylated alcohol benzoates are included as emollients and vehicles for the composition. See also U.S. Pat. No. 4,126,679 (Davy et al.). Unfortunately, these sticks cannot be formulated into an attractive transparent appearance. The wax matrix and insolubility of the antiperspirant active render the stick opaque.
Gelled alcoholic sticks may be formulated in either of two ways. One method is to utilize an alkaline aluminum chlorhydrate-lactate complex as the active and combine this with sodium stearate as a gelling agent. For instance, U.S. Pat. No. 3,259,545 (Teller) reports a stick containing an aluminum antiperspirant active, sodium lactate and sodium stearate. U.S. Pat. No. 3,472,940 (Osipow et al.) obtains stable gelled alcoholic compositions through the use of sodium stearyl-2-lactylate. A second method for obtaining gelled alcoholic sticks involves use of an alcohol soluble aluminum chlorhydrate complex (e.g. an aluminum chlorhydrate-propylene glycol adduct) and dibenzaldehyde monosorbitol acetal as gelling agent. Illustrative is U.S. Pat. No. 4,518,582 (Schamper et al.) wherein solid transparent gelled sticks of the foregoing type are disclosed.
Although gelled alcoholic sticks in transparent form can be achieved, these formulations suffer certain disadvantages. The alkaline aluminum active-lactate complex with sodium stearate is not particularly effective because alkaline antiperspirant actives intrinsically have low efficacy. Alcohol soluble aluminum active complexes as found in Schamper et al. provide unstable sticks because of the instability of acetal gelling agents in the presence of acidic aluminum actives. Many of the foregoing compositions form sticks that are not completely hardenable, thereby resulting in a tacky feel.
Accordingly, it is an object of the present invention to obtain an antiperspirant composition in stick form having improved antiperspirant properties and physical characteristics.
In particular, it is an object of the present invention to obtain a stick that is transparent and exhibits improved antiperspirancy.
Another object of the present invention is to obtain a transparent stick of acceptable hardness to avoid a tacky feel when applied to skin.